1. Field of the Invention
The present invention relates to a method for intravascular laser coagulation of arteries, veins, aneurysms, vascular malformations and arteriovenous fistulas and to a catheter/optical fiber device for use with a laser in practicing the method.
2. Description of the Prior Art
The conventional treatment of conditions such as intracranial and other arterial aneurysms, arteriovenous fistulas, etc., involves major surgery and the use of clips or ties. For example, in the treatment of a ruptured intracranial aneurysm, a craniotomy is performed and the aneurysm neck is ligated. U.S. Pat. No. 4,360,023 to Sugita et al, U.S. Pat. No. 4,340,061 to Kees et al and U.S. Pat. No. 4,484,581 to Martin, for example, disclose various clips designed for sealing off the neck of an aneurysm. However, the unsuitability of certain patients for surgery and other logistical considerations often prevent this conventional surgical approach. In particular, in the case of patients who have suffered an aneurysmal subarachnoid hemorrhage and in patients exhibiting rebleeding after such a hemorrhage, the need exists for a safe and more expeditious treatment.
The prior art has also proposed various devices intended for precisely positioning intravascular occlusions as a therapeutic approach to the treatment of certain types of vascular disorders. For example, Handa et al in U.S. Pat. No. 4,346,712 disclose a balloon catheter for the embolization of vascular lesions. With the device of Handa et al, after inflation of a balloon to embolize the vascular lesion, the balloon is released from the tip of the catheter by heat.
Laser probes have been rather widely used for the cauterization of internal vessels, particularly in ophthalmic surgery. U.S. Pat. No. 4,537,193 to Tanner exemplifies a prior art disclosure of such a laser probe.
The prior art has also proposed the use of fiber optic laser catheters for use in various therapeutic procedures. See U.S. Pat. No. 4,519,390 issued to Horne and an article coauthored by the present inventor entitled "Transcatheter Fiber Optic Laser Coagulation of Blood Vessels," Radiology, Vol. 142, No. 3, pp. 777-780 (March 1982). That Radiology article reported the results of experimental work on rabbit ears which demonstrated that, with ues of a laser beam emanating from a flexible optical fiber within an artery, focal coagulation of the artery at a predetermined site was achieved in six out of ten experiments. The article suggested the possible application of such a technique in the treatment of a ruptured intracranial aneurysm. However, with such a technique, the potential exists for injury to other tissue in the vacinity of the target site, i.e. the neck of the aneurysm. The article also reviews various other prior art approaches to the treatment of aneurysms including the injection of foreign substances such as hairs and iron-acrylic material into the aneurysm and the intraluminal introduction of an inflatable balloon into the aneurysm cavity by means of a "superselective" catheterization of the cerebral arteries.
The use of fiber optic laser catheters has also been proposed for the recanalization of occluded vessels. Choy in U.S. Pat. No. 4,207,874 discloses such a catheter device which is intended to function by utilizing a laser beam to burn a hole through a thrombus occluding an internal vessel. However, again, such a technique presents the attendant problem of the potential for trauma to healthy tissue. Abela et al in "Hot Tip: Another Method of Laser Vascular Recanalization," Lasers in Surgery and Medicine, 5:327-335 (1985) propose use of a somewhat refined device for vascular recanalization. The device of Abela et al, like that of Choy, includes a laser, a catheter and fiber optics. However, the device of Abela et al further includes a metal cap on the distal end of the optical fiber which is heated by the laser energy. Thus, the device of Abela et al uses the heated metal tip, rather than a laser beam to burn through the thrombus and thereby avoids the potential problem of the laser beam damaging healthy tissue.